Stackedit.io provides live preview of your Markdown syntax together with the formatted content, allowing one to update the Markdown syntax and view the changes instantly.

As for GitHub Gist, live previews are provided in a separate tab for comments on GitHub. The actual gists do not allow for one to preview the formatting of the Markdown syntax. But it would be familiar to get used to the GitHub interface, as we would use it for the creation of the website later.

Markdown supports the syntax highlighting of keywords in programming languages.

By enclosing the code block in 3 back-ticks (```) at the beginning and end of the code block and indicating the programming language after the initial 3 back-ticks, the syntax of the code will be highlighted as expected.